Does a pregnant woman with Group B Streptococcus (GBS) in her urine require treatment to prevent transmission to the newborn?

Treatment of GBS Bacteriuria During Pregnancy

Yes, any concentration of Group B Streptococcus (GBS) detected in urine during pregnancy must be treated immediately at diagnosis, and the patient must receive intravenous intrapartum antibiotic prophylaxis during labor regardless of whether the UTI was treated earlier in pregnancy. 1, 2

Why GBS Bacteriuria Requires Treatment

GBS in urine at any concentration is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 1, 2 The CDC guidelines emphasize that pregnant women with GBS bacteriuria are at substantially higher risk—more than 25 times more likely—to deliver infants with early-onset GBS disease compared to non-colonized women. 1

Two-Step Treatment Approach

Step 1: Treat the Acute UTI Immediately

• Treat the urinary tract infection according to standard pregnancy UTI protocols using pregnancy-safe antibiotics based on susceptibility testing. 2, 3
• Common first-line oral agents for outpatient treatment include penicillin or ampicillin (specific dosing should follow standard UTI treatment protocols). 2
• Critical caveat: Treating the UTI does NOT eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical. 2, 3

Step 2: Mandatory Intrapartum IV Prophylaxis During Labor

All pregnant women with GBS bacteriuria at ANY point during the current pregnancy must receive IV antibiotic prophylaxis during labor, even if the UTI was treated months earlier. 1, 2

Preferred Intrapartum Regimen (No Penicillin Allergy):

• Penicillin G: 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery 1, 2, 3
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery 1, 2

For Penicillin-Allergic Patients:

Non-high-risk allergy (no history of anaphylaxis, angioedema, or urticaria):

• Cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery 1, 2

High-risk allergy (history of anaphylaxis or severe reactions):

• Clindamycin 900 mg IV every 8 hours until delivery (if isolate confirmed susceptible) 1, 2
• Vancomycin 1 g IV every 12 hours until delivery (if resistant or susceptibility unknown) 1, 2

Critical Timing for Maximum Effectiveness

Intrapartum prophylaxis must be administered at least 4 hours before delivery for maximum effectiveness. 1, 2 When given ≥4 hours before delivery, prophylaxis is 78% effective in preventing early-onset neonatal GBS disease. 1, 2

Important Management Points

• Women with documented GBS bacteriuria at any point in pregnancy do NOT need repeat vaginal-rectal screening at 35-37 weeks—they are presumed to be GBS colonized and automatically qualify for intrapartum prophylaxis. 1, 2
• Laboratories should report GBS at concentrations ≥10,000 CFU/mL (≥10⁴ CFU/mL) when urine specimens are from pregnant women. 1, 2
• Even low colony-count GBS bacteriuria (<10⁴ CFU/mL) has been associated with elevated risk for early-onset GBS disease in some studies, though the evidence is less robust. 1

Common Pitfalls to Avoid

Never assume that treating the UTI eliminates the need for intrapartum prophylaxis—this is a dangerous and common error. 2 Oral or IV antibiotics given before labor are completely ineffective at eliminating GBS colonization and do not prevent vertical transmission during delivery. 1, 2

Do not use oral antibiotics to attempt GBS eradication before labor—such treatment is ineffective and may cause adverse consequences including antibiotic resistance. 1, 2, 3

Exception: Cesarean Delivery

Intrapartum prophylaxis is not needed if cesarean delivery is performed before onset of labor on a woman with intact amniotic membranes, as the risk for transmission is extremely low in this scenario. 1, 3